1. Field of the Invention
The present invention relates to a light guide capable of transferring light from an illuminating apparatus to a certain destination, and in particular to a light guide having an epicycloid cross section of a guide.
2. Description of the Background Art
Generally, an illuminating apparatus having a channel shape light guide capable of redistributing light from an illuminating apparatus through a lateral surface is directing to illuminating light to a wall surface of a guide based on a light flux which is smaller than an illuminating apparatus which does not have a light guide. The channel shape light guide must satisfy the following condition for being effectively used for various illuminating purposes.
1. The distributing of a light flux emitted to a guide must provide a necessary distribution of an illuminating parameter which requires a constant property and amount for an illuminated object in a direction and angle.
2. The power consumption must be prevented compared to other illuminating unit.
3. A certain gain must be obtained compared to other technical unit in view of cost.
As an illuminating apparatus having a channel type light guide, in a plurality of patents which are not actually used in all types of illuminating apparatuses, a front portion of a light guide is formed in a circle (concluding a certain convex portion) or polygonal shape for optical and structural schemes of a channel light guide. A light reflection unit having a lamp is formed in circle and is aligned with a hole of a channel type light guide.
A circular and polygonal light guide channel do not provide effective distribution of the emission through the stretch part of the light guide irrespective of a material used for a light guide having a mirror reflection or transparently prismatic or light scattering effect. In addition, a light distribution characteristic which must be changed in accordance with various applications cannot be changed. A plurality of patents concerning geometrical variations of prisms along the length of a light guide, a modification of a light guide, and a light emission parameter cannot optimize an illuminating apparatus under a required conditions.
It is necessary to concentrate (compress) scattered light from a light guide at a certain portion. In order to overcome the above-described problem, a method was suggested that alternately arranged a plurality of lenses in the longitudinal direction of the light guide and changed the optical characteristic of a light guide wall.
FIGS. 1A and 1B illustrates a prism installed at a wall surface of a light guide having a circular cross section. As shown in the structure of a light guide of FIG. 1A, a reflection cover is installed around a bulb 3 for concentrating light from the bulb 3 at a certain front portion, and a guide 1 is connected to transfer the light to a certain destination at the front surface of the reflection cover. A cap 2 is engaged at the end of the guide. As shown in FIG. 1B which illustrates the cross section of the light guide, the shape of the cross section is circular, and an engaging portion 5 is formed at the upper portion of the same. The guide is formed of an external guide 4 and an internal guide 9. The inner material is formed of a structured prism. FIGS. 2A and 2B illustrate the shape of the prism. As shown in FIGS. 2A, an isosceles triangle is continuously formed on the prism thin film, and FIG. 2B illustrates the size of the same. The guide using the prism is capable of fully-reflecting the light inputted at a certain angle. FIG. 2C is a perspective view illustrating a part of the guide having the prism.
However, it is practically impossible to basically overcome the problems of a channel type light guide by changing the optical characteristic of a light guide wall alternately arranging the lenses or using the prism. The above-described problem overcoming method may increase the cost of the channel type light guide. Therefore, the structure of the light guide channel and the optical connection with the light radiating unit must be improved.
Accordingly, it is an object of the present invention to provide a light guide capable of increasing efficiency and reducing fabrication costs without using a lens or prism like the conventional light guide.
In order to achieve the above object, in the present invention, the epicycloid type light guide is provided such that a cross-section of the guide is formed in a pipe shape having an epicycloid curve.